To achieve higher dynamic resolution of laser heterodyne interferometry, a new signal
processing method based on digital delay line technology is proposed. To implement
ultra-multiple electronic subdivision, the multiple frequency of the reference signal
which is generated from an analog phase-lock loop is passed through a multi-tap
digital delay line. On every positive edge of the measurement signal, each tap of the
delay line is captured and decoded to obtain the exact occurrence time. And according
to the reference period, the system can also provide a real time output of the
displacement results. Simulations and experiments show that using a laser heterodyne
interferometry with its beat frequency of 1MHz, the system can provide a dynamic
position resolution of 0.83nm at velocities up to 260mm/s by using a 64 multiple
analog phase-lock loop and a 6-tap digital delay line, the update rate of the
displacement positions is up to 100KHz.
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